Brocade Mobility RFS7000-GR Controller System Reference Guide (Supporting software release 4.1.0.0-040GR and later) - Manual (Page 22)

8 Brocade Mobility RFS7000-GR Controller System Reference Guide
53-1001944-01
Software overview
1
802.11bg
• Dual mode b/g protection – ERP builds on the payload data rates of 1 and 2 Mbit/s that use
DSSS modulation and builds on the payload data rates of 1, 2, 5.5, and 11 Mbit/s, that use
DSSS, CCK, and optional PBCC modulations. ERP provides additional payload data rates of 6,
9, 12, 18, 24, 36, 48, and 54 Mbit/s. The transmission and reception capability for 1, 2, 5.5,
11, 6, 12, and 24 Mbit/s data rates is mandatory.
Two additional optional ERP-PBCC modulation modes with payload data rates of 22 and 33
Mbit/s are defined. An ERP-PBCC station may implement 22 Mbit/s alone or 22 and 33
Mbit/s. An optional modulation mode (known as DSSS-OFDM) is also incorporated with
payload data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbit/s.
• Short slot protection – The slot time is 20 µs, except an optional 9 µs slot time may be used
when the BSS consists of only ERP STAs capable of supporting this option. The optional 9 µs
slot time should not be used if the network has one or more non-ERP STAs associated. For
IBSS, the Short Slot Time field is set to 0, corresponding to a 20 µs slot time.
Rate limiting
Rate Limiting limits the maximum rate sent to or received from the wireless network per mobile
unit. It prevents any single user from overwhelming the wireless network. It can also provide
differential service for service providers. The uplink and downlink rate limits are usually configured
on the RADIUS server using Brocade vendor specific attributes. The switch extracts the rate limits
from RADIUS server response. When such attributes are not present, the global settings on the
switch are then applied.
Proxy-ARP
Proxy ARP is provided for MU's whose IP address is known. The WLAN generates an ARP reply on
behalf of a MU (if the MU's IP address is known). The ARP reply contains the MAC address of the
MU (not the MAC address of switch). Thus, the MU does not awaken to send ARP replies (increasing
MU battery life and conserving wireless bandwidth).
If an MU goes into PSP without transmitting at least one packet, its Proxy ARP will not work.
HotSpot / IP Redirect
A hotspot is a Web page users are forced to visit before they are granted access to the Internet.
With the advent of Wi-Fi enabled client devices (such as laptops and PDAs) commercial hotspots
are common and can be found at many airports, hotels and coffee shops. The hotspot re-directs
the user’s traffic on hotspot enabled WLANs to a web page that requires them to authenticate
before granting access to the WLAN. The following is a typical sequence for hotspot access:
1. A visitor with a laptop requires hotspot access at a site.
2. A user ID/ Password and hotspot ESSID is issued by the site receptionist or IT staff.
3. The user connects their laptop to this ESSID.
4. The laptop receives its IP configuration via DHCP.
5. The user opens a Web browser and connects to their home page.
6. The switch re-directs them to the hotspot Web page for authentication.
7. The user enters their User ID/ Password.